For a tube you might have to duplicate, I like Phil's methods.

But there are some questions you need to answer. If the outside of the tube is a critical dimension, build it inside a pipe. If the inside dimension is critical, build it over a mandrel.

I have used Phil's wax over aluminum tube except I use multiple layers of wax paper. I like wax paper because it's easy and I can build it up to a dimension, if I have to. I like aluminum because a 3 or 4 mm wall Al tube does not deform under the couple of psi of vacuum bagging. USE MULTIPLE SEPARATE LAYERS OF WAX PAPER. DON'T TAPE THE WAX PAPER TO THE TUBE, IT IS HARD TO GET IT TO RELEASE.

For vacuum bags I use nylon tubes from fiberglass supply company

I have not used the inside of a pipe method but, it is similar to what I have seen used. They started with a mandrel a foot or so longer than the mold. The mandrel was split into 4 or 6 sections with a pipe in the middle and held together with tape. They put a bag over the mandrel and then wound felt to about the right inside diameter. They wound release fabric over the felt and then put down their layout. They used 10 oz 45x45 cloth for the layup and it went fast. Two guys rolling epoxy on and 1 guy rolling the cloth. They wrapped the layup with stretchy film and clamped the pipe around it. Then they inflated the bag around the mandrel just enough to get the mandrel out. The mandrel is split with a pipe in the middle so if it's a bad day you can still get it out and you can vary the mandrel diameter by changing the diameter of the pipe. They inserted a heavier bag, positioned it and inflated it to about 5-10 psi. Then they popped the whole thing into an oven and waited. This was not a high tech setup. However they were very neat, clean, and carefull.